Thermostatic electric switch



June 19, 19.28. 1,674,151

J. W. ANDERSON THERMOSTATIC ELECTRIC SWITCH Original Filed April 14, 1926 In ventot: Jo/m W fl/m ersa z Patented June 19, 1928.

UNITED STATES JOHN W. ANDERSON, F HAMILTON, ONTARIO, CANADA.

THERMOST ATIC ELECTRIC SWITCH.

Application filed April 14, 1926, Serial No. 102,041. Renewed April 28, 1928.

The principal object of this invention is to provide a very simple and positive operating electric switch for controlling the operation of a motor through the effect of temperature conditions, and particularly to prov de a switch for controlling the driving motor of a refrigerating device.

The principal feature of the invention consists in the novel construction of a switch member, whereby a reciprocable memberis operated to move into and out of contact with electric terminals in an instantaneous movement effected by the snap action of a spring actuated lever member, which lever member is controlled by a thermostatically affected member.

In the drawings, Figure 1 is aside elevational view. of a switch constructed in accordance with this invention.

Figure 2 is a plan view in part section.

Figure 3 is a vertical cross sectional view through the line 33 of Figure 1.

In the automatic operation of a switch for controlling an electric power circuit, it is important that the movement of the switch arm making the electrical connection be very rapid and as thermostatic devices move very slowly it is a somewhat diflicult'problem to obtain the fast movement of a switch 30 member from the slow action of a thermostat.

In the present invention the thermostat is in the form of a circumferentially corrugated cylinder of thin metal 1 which has great longitudinal elasticity. This cylinder is filled with methyl chloride gas which is very sensitive to temperature conditions and expands ver rapidly as the liquid methyl chloride boil s at a temperature of about fourteen degrees below zero.

The cylinder is secured at its base to a plate 2 and supported above the plate 2 by ,means of the posts 3 is a plate 4 arranged above the top and clear of the cylinder 1.

A stem 5 is secured tothe top of the cylinder 1 and extends upwardly through a hole in the top plate 4 and the upper end thereof is slotted to'receive the end of a lever 6 which is pivoted on the pin 7.

A air of rigid supports 8 are secured to the p ate 4 adjacent to the stem 5 and carry the fulcrum 9 of the lever 6 arranged as close as possible to the pivotal oint of connection between the lever and t e stem 5.

A pair of brackets 10 are secured to the underside of the plate 4 and said brackets support the paired bell crank levers 11 pivoted on the pins 12.

A link 13 adjustably connected to the free end of the lever 6 is adjustably connected to the horizontal legs of the bell crank levers 11 by a pin 14.

A pin 15 is rigidly secured in the brackets 8 above the pivotal supports of the levers 11 and a pin 16 connects the lower ends of the levers.

A coil tension spring 17 connects the pin .16 with the pin 15.

It will be seen that when the downwardly extending legs of the bell crank levers move to a position out of the vertical the tension of the spring 17 will throw the lever with a snap movement in whichever direction past the centre line it is moved.

A pair of slotted standards 18 are secured tothe base plate 2 and are set to one side of the plane of movement of the said bell crank levers.

A bar 19 is slidably supported in the slotted standards-having slots 20 to limit the longitudinal movement and pins 21 and 22 are rigidly secured in said bar to the forward and back ends thereof which pins extend into the plane of movement of the bell crank levers to be kicked thereby.

An electric contact plate 23 is mounted on an insulating block 24 on one end of the bar 19 and a pairof spring terminals 25 are secured to an insulating plate 26 rigidly secured between the top and bottom plates of the structure.

In the operation of the device when the temperature surrounding the thermostat member reaches a predetermined high point, the methyl chloride will have expanded and pushed upwardly on the stem 5 to tilt the lever 6 and the bell crank 11 to swing the same forwardly until the tension spring connected to the bell crank lever is moved past the vertical. The spring then throws the bell crank lever forwardly with a snap to strike the forward pin 21 on the bar 19,

thereby closing the switch to start the electric mechanism with which the switch is connected. 7 I

As the temperature surrounding the thermostat falls the the thermostat contracts and pulls downwardly on the short end of the lever, thereby swinging the bell crank with its vertical portion in a rearward direction and when it passes the vertical centre the spring snaps the lever over so that it engages the rearward pin 22 of the bar 19 with a kicking action suflicient to withdraw it suddenly from engagement with the spring contacts, thus breaking the electrical connection. I

It will be understood that while there is no loose play in the connections between the bell crank lever and the thermostat the action of the spring 17 is suificiently strong to throw the bell crank lever with a sharp movement as the flexible thermostat tube will yield readily either to sufficient expansion or contraction to allow of the requlred movement.

What I claim as my invention is:

1. In a thermostatic electric switch, the combination with a thermostat of a pair of contacts, a slidable switch member adapted to bridge said contacts, a spring actuated snap action 'pivotal member adapted to strike said switch member tothrow it into or out of engagement with said contacts,

and means operatively connecting said snap action member with the thermostat.

2. In a thermostatic electric switch, the

combination with a thermostat, of a pair of contacts, a reciprocable switch member adapted to bridge said contacts and having a pair of spaced projections, a spring actuated snap action member adapted to engage the spaced project-ions of said reciprocable member to move it intoand out of engagement with said contacts, and a lever oper operatively connecting the thermostat and with said bell crank lever.

4. In a thermostatic electric switch, the combination with a corrugated tubular thermostat containing a thermal gas, of a frame extending around said thermostat, a lever pivoted on the frame and pivotally connected to said vthermostat, a bell crank lever pivoted in the 'frame, a link connecting said lever and said bell crank lever, areciprocable switch member slidably supported in the plane of movement of the bell crank lever, a spring adapted to actuate said bell crank lever to swing past the centre in either direction, means on said switch member adapted to be engaged by said bell crank, and a pair of electrical contacts adapted to be closed by said switch member.

JOHN W. ANDERSON. 

